Calculation of flooding through urban flash floods. The hydraulic simulation of the surface runoff in case of a canalization overload is done by means of a 2-dimensional calculation approach. The spatial extent, the chronological progression and the water depth of flooding may be analyzed. Precautionary measures may be deduced from the analysis and verified for their effectiveness.
“Urban flash floods” is the itwh software package for the calculation of flash floods caused by heavy rainfall. The package contains the 2-dimensional surface runoff model HYSTEM-EXTRAN 2D and FOG for the administration of sewer system models as well as FOG 2D for the creation of the terrain model in ArcGIS.
Exceptionally heavy rainfall events lead to the overload of sewer systems with the implication that flash floods with negative impacts on urban infrastructure or even danger to life can occur. With the itwh software package “urban flash floods” the hazards of heavy rainfall can be analyzed in detail. Through the linkage of the sewer system model HYSTEM-EXTRAN with the 2-dimensional surface runoff model HYSTEM-EXTRAN 2D a detailed simulation of the runoff processes in the sewer system and on the surface is made.
may be analyzed and visualized.
In the calculation the sewer system model HYSTEM-EXTRAN and the 2D model HYSTEM-EXTRAN 2D of the surface are linked bidirectionally through manholes and street inlets. The water leagage from the sewer system through overflow, as a result of the overload of the sewer system, as well as the reentry, if capacities are available, are visualized in detail. The results of the calculations may be visualized and classified to assess the entent of potential damage through flash floods. This in turn forms the basis for a risk assessment acording to DWA-M 119.
The menu navigation in the itwh software package “Urban flash floods” is workflow-oriented: All required tool are included, starting with the data preprocessing as well as the automated creation of the calculation model up to the visual evaluation of the results.
The sewer system model and the 2D surface runoff model are coupled together. The coupling takes place at the manholes and street inlets. As a result of the linkage of both models, in conjunction with the extensive calculation approach, a realistic model is formed. In contrast to other hydrological models, depressions and hollows are implicitly considered.
Various versions of the sewer system- and 2D surface runoff model may be combined for the simulation of planning options (the use of linkage manholes with the same name is a prerequisite).
The calculation approaches of HYSTEM-EXTRAN 2D are visualized in FOG 7. The water levels may be displayed in a chronological sequence for the output steps. The chronological sequence of the simulated flood may also be displayed as a video clip (*.avi file).
…the software package “Urban flash floods” naturally takes into account the conventional guidelines, such as the DWA working paper A 119 and the DIN EN 752.
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